Ferroelectric liquid crystal displays offer great advantages in terms of quick response, the time needed for a change in orientation of the ferroelectric liquid crystal array being much shorter than the time needed for the change in a typical nematic liquid crystal. One advantage of this quick response is that sequential coloring of pixels is possible at a refresh rate that facilitates color fusion, that is, the appearance to the human eye of the pixel as a single color rather than as rapidly sequentially changing colors. Sequential color also enables greater resolution for a particular pixel size, as a single pixel can display all colors, rather than requiring three pixels, red, green and blue, to display a full color spectrum.
One phenomenon of liquid crystal displays, such as those of the ferroelectric type, is termed “image sticking” (also known as “optical hysteresis” or “ghost images”), referring to a residual image that is displayed on the screen persisting long after the driving voltages are removed from the ferroelectric liquid crystal (FLC) pixels. Charge densities are especially high in FLC devices because of the spontaneous polarization and the resulting internal electric fields. In sequential color ferroelectric liquid crystal on silicon (FLCOS) devices, a DC offset in the drive algorithm may cause severe sticking, but operation in a DC balanced mode can reduce image sticking. DC balancing refers to the process wherein a voltage of inverse polarity is applied to a liquid crystal pixel immediately following application of a display voltage to assist in neutralizing residual electrical charges that may be responsible for image sticking. However, this mode of operation turns off the LEDs supplying the light modulated by the FLCs during the balance phase when the inverse polarity voltage is applied, thereby reducing the light output of the device. For more information, see U.S. Pat. No. 6,075,577, incorporated herein by reference in its entirety.
Images are produced on an FLC display by applying a suitable pattern of voltages to the display's pixels and viewing the resultant pattern of FLC optical states using crossed polarizers. In standard video systems the displayed image changes at a rate of 60 frames per second. Under certain conditions an image can become “stuck” for a time, so that when subsequent images are displayed, the stuck image is superimposed on those later images.